For years, Gerry Tobin had worn the infamous death's head insignia of a Hells Angel with fierce pride and unquestioning loyalty. Thousands of bikers across Britain aspire, but only 250 have reached the status of a "fully patched" member of the revered and reviled motorcycle club. But 35-year-old Mr Tobin's treasured patch would become his death warrant.

After a weekend of hedonism and revelry at the Hells Angels' annual Bulldog Bash festival, he rode back home along the M40, unaware rival gang members lay in wait, preparing for his "cold-blooded execution".

For some time, the Outlaws – a gang whose bitter antagonism towards Hells Angels is steeped in decades of bloodshed – had been meticulously planning the killing. As Mr Tobin cruised down the motorway, two shots were fired at him from a passing Rover. One bullet skimmed the base of his helmet, lodging in his skull and killing him instantly.

Yesterday, seven men, the entire South Warwickshire chapter of the Outlaws, were jailed for life for the murder of a man referred to as Gentleman Gerry by his friends. "This was an appalling murder," said Judge Mr Justice Treacy in Birmingham Crown court. "A totally innocent man was executed with a firearm in broad daylight on a busy motorway for no reason other than that he belonged to a different motorcycle club than yours. He was a total stranger to you. The utter pointlessness of what you did makes his murder more shocking."

But Mr Tobin had strayed on to what the Outlaws believed was their territory. For some time, the rival gang had stewed over what they viewed as a "provocative" move by the Hells Angels to hold their annual festival in Long Marston in their heartlands of Warwickshire, Staffordshire, Derbyshire and Birmingham. Nine years earlier they had threatened to bomb the event and, in 2001, a Hells Angel leaving the bash was shot three times in the leg from gunmen in a dark-coloured saloon. The victim survived but refused to make a complaint. Again, this time, neither victims nor perpetrators were willing to help police investigating Mr Tobin's death. The notorious code of the "one per center" gangs – coined in response to the American Motorcyclist Association's famous comment that 99 per cent of bikers were law-abiding citizens – prevailed and they stayed silent.

The hit, police believe, had been authorised within the upper echelons of the Outlaws in the United States, and the gang had been working out the finer details for some time. At their Christmas party in an art deco watering hole on the fringes of Coventry, the president, serjeant-at-arms and a bespectacled treasurer had been among those gathered to plot the death of a rival gang member they callously dismissed as a "maggot".

The chapter's president Sean Creighton, 44, who would fire the fatal shot, began target practice on a dummy at his home nearby. Three days before the murder, the men began monitoring bikers heading for the Bulldog Bash, looking out for a member of the Hells Angels.

They found one. On the day in question, as Mr Tobin, a mechanic, rode his Harley-Davidson down the motorway, a green Rover sped up beside him at 90mph. Its driver Dane Garside, 42, said to be the vice-president, manoeuvred it into position and Creighton and Simon Turner, 41, the chapter's serjeant-at-arms opened fire. Nearby, Dean Taylor, 47, as well as "dogsbody probationers" Karl Garside, 45, and Ian Cameron, 46, were acting as back-up in a white Range Rover and Malcolm Bull, 53, was patrolling in a Renault Laguna. Minutes after the murder, the occupants of the Rover ordered their two sub-units to stand down. They sped back to the Coventry area and the Rover was set alight in a country lane.

Creighton pleaded guilty to the killing but the rest maintained their innocence through the nine-week trial until they were convicted of the murder and related firearms offences. Yesterday all seven stood, handcuffed, in the dock, as the judge sentenced them. Outside the court, 100 fellow Outlaws waited as armed police officers kept a watchful eye.

Creighton was told he would locked up for a minimum of 28 years and six months, Turner for 30 years, Bull, 25 years, Dane Garside, 27 years, Taylor, 30 years, Karl Garside, 26 years and Cameron for 25 years. "None of you has showed the remotest feeling, consideration or remorse for what you did," the judge said. "This dreadful crime, in my judgment, falls into a particularly high category of seriousness because it involved the use of a firearm and because of its cold-blooded and ruthless nature." He said Mr Tobin's fiancée, 26-year-old Rebecca Smith, had had her hopes of marriage and family shattered, and his parents still found it difficult to come to terms with the "cold-blooded execution" of their only son.

The men share a history of violence. Turner had been jailed for throwing petrol over a stranger and stabbing him, Dane Garside had been involved in an axe attack 18 years ago and his brother Karl had previous convictions including battery, taking a knuckleduster to court and grievous bodily harm. Bull was described by the judge as a "wicked criminal".

Most tellingly, more than 20 years ago, Taylor was charged with aggravated burglary after he and seven other men travelled to Leicester with three sawn-off shotguns over a dispute with the Hells Angels. The hatred between the Hells Angels and the Outlaws – the former created in California in 1948 and the latter in Illinois in 1935 – has festered in a world where criminality, drugs and violence have been commonplace.

It all started with the 1969 rape of the wife of a Hells Angel by an Outlaw. Her husband and other Angels beat the rapist to death, then three Hells Angels were kidnapped, killed and their bodies thrown into a Florida quarry. And the murders continue: in 2006, an Outlaws security chief in New Hampshire killed a man wearing a Hells Angels shirt.

The violence spilled across the world. Hells Angels opened a chapter in Britain in 1968 after a couple of members were invited to London by the Beatles. But it was not until 2000 that the UK Outlaws club was recognised by the American parent body.

Mr Tobin's murder may have been retaliation for another killing elsewhere, police say, but the true reason is shrouded in secrecy. "They do not talk to us, as witnesses and victims, so sometimes we do not know what is really going on," said Detective Superintendent Ken Lawrence, who led the Tobin murder inquiry. "There were other events last year in August about the same time he was murdered, one in Sweden and North America. It's difficult to link one attack to another because they are going on all the time."

In 1998, there were fears biker wars would break out in Britain after two members of the Outcasts – which merged with the Outlaws – died at the hands of Hells Angels in Battersea, south London. In January this year, three Outlaws were attacked by a gang of Hells Angels with machetes at Birmingham airport in front of passengers and children.

This year, police tried to prevent the Bulldog Bash. At the licence application meeting, Assistant Chief Constable William Holland said: "The clear evidence from this country and abroad is that the Hells Angels and the Outlaws are organised crime groups. What we have evidence of is increasing tension between the Hells Angels and the Outlaws."

What happens now remains to be seen. As the Outlaws slogan states: "God forgives, Outlaws don't." Nor, one might imagine, do Hells Angels.

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